19.1 Technical Overview

conn_throttle.so is a shared library used as a callout
from the MTA's mapping table that uses an in-memory table of incoming connections
to determine when a particular IP address has recently connected too often
and should be turned away for awhile. While having an in-memory table is good
for performance, its largest cost is that each individual process on each
server maintains its own table.

In most cases, the conn_throttle.so callout is done
in the PORT_ACCESS mapping that is accessed by the Dispatcher,
a single process on each system. The only cost is that there is a separate
table per server.

The primary improvement by MeterMaid is that it maintains a single repository
of the throttling information that can be accessed by all systems and processes
within the Messaging Server environment. It continues to maintain an in-memory
database to store this data to maximize performance. Restarting MeterMaid
will lose all information previously stored, but since the data is typically
very short lived, the cost of such a restart (done infrequently) is very low.